diff --git a/cibuildwheel/macos.py b/cibuildwheel/macos.py
index 2a3b1881..0426441c 100644
--- a/cibuildwheel/macos.py
+++ b/cibuildwheel/macos.py
@@ -236,7 +236,15 @@ def setup_python(
     # ensure we have the version that matches our constraints
     # use "--force-reinstall" ensures that it's installed as 'pip'
     call(
-        ["python", "-m", "pip", "install", "--force-reinstall", "pip", *dependency_constraint_flags],
+        [
+            "python",
+            "-m",
+            "pip",
+            "install",
+            "--force-reinstall",
+            "pip",
+            *dependency_constraint_flags,
+        ],
         env=env,
         cwd="/tmp",
     )
diff --git a/cibuildwheel/windows.py b/cibuildwheel/windows.py
index addd3bc0..42dfc85d 100644
--- a/cibuildwheel/windows.py
+++ b/cibuildwheel/windows.py
@@ -180,7 +180,15 @@ def setup_python(
     # ensure we have the version that matches our constraints
     # use "--force-reinstall" ensures that it's installed as 'pip.exe'
     call(
-        ["python", "-m", "pip", "install", "--force-reinstall", "pip", *dependency_constraint_flags],
+        [
+            "python",
+            "-m",
+            "pip",
+            "install",
+            "--force-reinstall",
+            "pip",
+            *dependency_constraint_flags,
+        ],
         env=env,
     )